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DIMORPHISM OF THE GAMOBIUM 



367 



(ovy). Thus although there is no difference in the spores, 

 the prothalli produced from them are of two distinct kinds, 

 the smaller being exclusively male, the larger female. 



FIG. 84. Reproduction and Development of Equisetuin. 



A, distal end of a fertile shoot, showing two leaf-sheaths (/. sh), and 

 the cone formed of hexagonal sporophylls (sp. pit). (Nat. size.) 



B, diagrammatic vertical section of a portion of the cone, showing the 

 sporophylls (sp, pli) attached by short stalks to the axis of the cone, and 

 bearing sporangia (spg) on their inner surfaces. 



C, a male prothallus bearing three spermaries (spy). ( x 100. ) 



D, portion of a female prothallus bearing three ovaries (ovy), those to 

 the right and left containing ova, that in the middle a polyplast ; rh, 

 rhizoids. ( x 30.) 



(A, after Le Maout and Decaisne ; c and D, after Hofmeister. ) 



The oosperm develops in much the same way as in 

 ferns : it divides and forms a polyplast, which, by formation 

 of a stem, root, foot, and two cotyledons, becomes a 

 phyllula and grows into the adult plant. 



